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Fixing instrument for use in spinal surgery

  • US 4,827,918 A
  • Filed: 05/06/1987
  • Issued: 05/09/1989
  • Est. Priority Date: 08/15/1985
  • Status: Expired due to Fees
First Claim
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1. A fixing instrument for securing two vertabrae in fixed relative positions during spinal surgery, comprising:

  • a. a screw spindle having a threaded portion;

    b. first and second support members rotatably mounted on said screw spindle, said second support member having a threaded bore threadably engaged with said threaded portion of said screw spindle so that rotation of said screw spindle relative to said first and second members causes said first and second support members to move relative to one another along the length of said screw spindle, each of said support members including a stud fixed thereto, said stud having an axis substantially perpendicular to the length of said screw spindle, each of said studs including a transverse slot having axially opposed side walls and extending radially through said stud;

    c. first and second bone screws; and

    d. first and second securing means for respectively securing said first and second bone screws to said first and second support members, each of said securing means including;

    a securing member pivotally mounted on said stud of said respective support member and having a locking hole aligned with said transverse slot of said respective stud, said securing member also including a surface portion facing said respective support member and a substantially cylindrical bone screw hole adjacent said surface portion for holding said respective bone screw, said bone screw hole having a central axis spaced from said surface portion by a distance less than the radius of said bone screw hole so that a peripheral portion of said bone screw held in said bone screw hole protrudes from said surface portion of said securing member, for permitting said peripheral portion of said respective bone screw to engage with said surface portion of said respective support member and thereby prevent movement of said bone screw relative to said respective support member, andlocking means movably disposed in said locking hole and said respective aligned slot for selectively restraining movement of said securing member relative to said respective support member, said locking means including a locking member having a tapered surface portion providing variable clearance between sid locking member and said side walls of said slot, said tapered surface portion having a maximum cross section engageable with both of said side walls to clamp said securing member to said respective stud and thereby engage said peripheral portion of said respective bone screw with the surface portion of the respective support member.

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